Biased pivoting cartridge extractor for blowback bolt firearms

ABSTRACT

A biased pivoting spent ammunition cartridge case extractor and retainer mechanism for blowback bolt firearms. The mechanism includes a distal arcuate hook shaped and dimensioned to intimately engage and nest into part of the circumferential groove in front of the cartridge rim. The hook remains engaged during blowback extraction of the casing from the chamber, and prior to ejection of the case from the firearm. The hook is formed onto the distal end of a rocking member secured to the bolt by a medial pivot. A compression spring bears against the opposite, proximal end of the rocking member thereby biasing the hook inwardly toward the counterbore seat on the distal end of the bolt into which the base of the case rests during extraction. A direct gas impingement system overcomes the biasing force of the spring to cause the case to be ejected.

PRIOR APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/397,817, filed 2016 Sep. 21, and U.S.Provisional Patent Application Ser. No. 62/397,812, filed 2016 Sep. 21,both of which are fully incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to firearms, and more particularly to automaticspent cartridge extraction mechanisms for blowback style firearms.

BACKGROUND

Most firearms provide mechanisms to facilitate the automated handling ofammunition and their waste products. A firing cycle can include thestages of: stripping an unfired ammunition cartridge from aspring-loaded multi-cartridge magazine; chambering the cartridge;firing; extraction of the spent cartridge casing from the chamber; and,ejection of spent cartridge casing from the firearm. A blowback boltmechanism uses some of the force of the pressurized gasses generated bythe burning propellant in the cartridge to accomplish operation of thecycle in an automatic or semiautomatic way.

It can be appreciated that spent cartridge casing extractors have beenused with blowback style bolt action firearms for many years. Typically,prior blowback style extractors have used a beam, or flexure-type, leafspring extraction mechanism.

An important problem with such mechanisms is that minor variations inbeam thickness due to manufacturing imprecision can cause deviations inbeam strength, thus changing the resiliency of the beam and the forcesit applies. It is understood that the strength of a beam changes by thecube of its deviation in thickness. Therefore, even very slight changesin thickness can adversely affect cartridge manipulation by theextractor mechanism during loading into the firing chamber, and duringcartridge casing ejection after firing due to deviation in energyabsorption or transmission.

Similarly, minor variations in the material characteristics of thesemechanical parts can adversely affect performance. Characteristics suchas material strength, coefficient of friction because of coating orsurface irregularities, and other material properties can similarlyadversely affect the resiliency properties of the beam.

Another problem with conventional blowback bolt extractors using thebeam bending design is that there is a narrow optimum range ofdeflection required to properly interface with the cartridge casingduring extraction and eventual ejection. It is often difficult toachieve such a narrow optimum range of operation due to vagaries inmanufacturing and/or assembly.

While conventional extractor designs may be suitable for preciselymanufactured, carefully assembled, and well-maintained firearms usingprecisely manufactured ammunition cartridges, they may not be suitablefor firearms that must easily operate over a wide range of cartridge andbolt tolerances, while still providing low force absorption duringloading, and positive and consistent retention during cartridge casingejection.

Rifles such as the AR-15 and M-16 firearms utilize a Direct GasImpingement (DGI) type of blowback extractor wherein the flow ofresidual firing gases provide the necessary force to extract the spentcartridge casing from the chamber and eject it off of the boltcounterbore at the appropriate time. Such designs are impractical in thenarrow confines of handgun type firearms.

Therefore, there is a need for an automatic spent cartridge casingextraction mechanism which better accommodates minor manufacturingvariation in cartridges and firearm parts, which better accommodateswear, and which better maintains alignment of the cartridge and boltduring chambering and extraction. There is a need for a cartridgeextractor mechanism which operates over a wide range of cartridge andbolt tolerances, which provides low force absorption during loading, andwhich provides positive and consistent retention of the cartridge priorto ejection from the firearm.

In other words, there is a need for an automatic spent cartridgeextraction mechanism which addresses some or all of the above identifiedinadequacies.

SUMMARY

The principal and secondary objects of the invention are to provide animproved cartridge extractor mechanism for blowback bolt firearms. Theseand other objects are achieved by a biased pivoting cartridge extractormechanism mounted to the bolt of the firearm.

In some embodiments there is provided a biased pivoting cartridgeextractor that will operate over a wider range of cartridge and bolttolerances with low force absorption during loading, and positive andconsistent retention of the cartridge during ejection from the firearm.

In some embodiments there is provided a biased pivoting cartridgeextractor pivotingly secured to an axially slidable bolt. In someembodiments the extractor has a cartridge contacting feature that isbiased radially inwardly toward the cartridge seat location on the boltby a compression spring located on the opposite end from the pivot. Insome embodiments a compression spring loads the extractor against thecartridge rim, and thus the cartridge rim against the cartridgecounterbore within the bolt.

In some embodiments there is provided a blow-back style of firearm boltmodified to accept a Direct Gas Impingement style of cartridgeextractor.

In some embodiments there is provided an extractor based in part on thestyle of an AR-15 or M-16 type of extractor to retain relative alignmentof the cartridge to the cartridge counterbore in the bolt duringcartridge ejection.

In some embodiments there is provided a cartridge extractor thatproperly engages a cartridge through a wide range of dimensionaltolerances for the bolt, extractor, and cartridge.

In some embodiments there is provided a cartridge extractor that is notgreatly impacted by material strength inconsistencies.

In some embodiments there is provided a cartridge extractor that is notgreatly impacted by deviations in the surface coefficient of friction.

In some embodiments there is provided a cartridge extractor that hasgreater resistance to cyclic fatigue.

In some embodiments it is provided that in a firearm having a boltreciprocatingly sliding axially along a bolt axis, said bolt temporarilyengaging an ammunition cartridge at a distal bolt seat during a firingcycle, wherein said ammunition cartridge includes a case portion havinga proximal rim adjacent to a circumferential groove, an improvementwhich comprises: an extractor assembly which comprise: an oblong rockingmember comprising a hook radially moveable with respect to said bolt;and, said oblong rocking member being pivotingly secured to said bolt ata pivot.

In some embodiments said hook is biased radially inwardly by a biasingforce.

In some embodiments said biasing force is overcomeable by an ejectorselected from the group consisting of a mechanical ejector, and directgas impingement of pressurized gaseous forces generated during saidfiring cycle.

In some embodiments said pressurized gaseous forces comprise a radialcomponent impacting said case portion during an ejection stage of saidfiring cycle.

In some embodiments the improvement further comprises a spring betweensaid bolt and said rocking member, said spring providing said biasingforce.

In some embodiments said rocking member comprises: a distal end portioncarrying said hook; a proximal end portion; and, a medial portionsecured to said pivot.

In some embodiments said spring comprises a first terminus bearingagainst said bolt and a second terminus bearing against said proximalend portion of said extractor member.

In some embodiments said pivot comprises a pivot pin defining anextractor axis of rotation; said pivot pin having a substantiallycylindrical post rotatively engaging a substantially cylindricalbearing.

In some embodiments said extractor axis of rotation is perpendicular tosaid bolt axis.

In some embodiments said rocking member moves within a recess formedinto said bolt.

In some embodiments said rocking member rocks within a plane angularlyinclined between about 66.5 degrees and about 68.5 degrees from verticalwith respect to the firearm in a upright orientation.

In some embodiments said hook comprises a concave arcuate tip shaped anddimensioned to intimately nest against a convex surface of saidcircumferential groove; and, wherein said concave arcuate tip is furtherdimensioned to have an axial dimension less than the axial dimension ofsaid circumferential groove.

In some embodiments said arcuate tip and curved outer surface of saidcartridge have commensurate radii of curvature.

In some embodiments said hook further comprises a pair of convex cornersat the angular extremities of said arcuate tip.

In some embodiments said bolt has a distal face having a counterboreseat and an axially proximally recessed lip adjacent to said seat on alower portion of said distal face.

In some embodiments it is provided that in a method for securing a spentammunition cartridge case against a seat of a bolt during a firing cycleprior to ejection of said case from a firearm, said cartridge casehaving a proximal rim adjacent to a circumferential groove, animprovement which comprises: contacting a proximal rim of said caseagainst said seat; and, simultaneously to said contacting, engaging saidcircumferential groove of said case by a hook of an extractor memberpivotingly mounted to said bolt.

In some embodiments the improvement further comprises radially biasingsaid hook against said case.

In some embodiments said radially biasing occurs with a forceovercomeable by direct gas impingement forces generated by during saidfiring cycle.

The text of the original claims is incorporated herein by reference asdescribing features in some embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic cross-sectional and partially enlarged sideview of a firearm having a blowback bolt having a pivoting cartridgeextractor according to an exemplary embodiment of the invention.

FIG. 2 is a diagrammatic perspective view thereof.

FIG. 3 is a diagrammatic, enlarged cross-sectional side view thereof.

FIG. 4 is a diagrammatic end view showing the angular location of theextractor on the bolt.

FIG. 4 is a diagrammatic, cross-sectional side view thereof duringcartridge firing and extraction.

FIG. 5 is a diagrammatic, cross-sectional side view thereof duringcartridge ejection.

FIG. 7 is a diagrammatic, perspective view of a blowback bolt having apivoting cartridge extractor according to an alternate exemplaryembodiment of the invention.

FIG. 8 is a cross-sectional view of the blowback bolt of FIG. 7 takenperpendicular to the pivot axis of the extractor.

FIG. 9 is a cross-sectional side view of the blowback bolt of FIG. 7 asa cartridge is being chambered.

FIG. 10 is a cross-sectional front view of the blowback bolt of FIG. 7showing the cartridge rim cartridge becoming seated in the counterboreseat.

FIG. 11 is a cross-sectional side view of the blowback bolt of FIG. 7showing the cartridge being stripped from the magazine for chambering.

FIG. 12 is a cross-sectional side view of the blowback bolt of FIG. 7showing the cartridge fully chambered.

FIG. 13 is a cross-sectional side view of the blowback bolt of FIG. 7showing the spent cartridge casing being ejected by a mechanicalejector.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

It is important to note that in the exemplary embodiments shown, manycritical firearm features, such as the firing pin, triggeringmechanisms, ejector mechanisms, and direct gas impingement channelinghave been omitted from some of the firearm illustrations in order toimprove clarity. Those skilled in the art will readily recognize wheresuch features can be expected to reside in a more complete illustration.

Further, the viewpoint of the cross-section in FIGS. 1, 5, and 6 istaken generally from a the side of the firearm. However, to properlyindicate the operation of the various features, their angular locationswith respect to the bolt axis have been adjusted to fall within thevertical plane. Those skilled in the art will readily appreciate thatsuch features can be located in angularly different locations in anoperational firearm.

Referring now to the drawing, there is illustrated in FIGS. 1 and 2, asemiautomatic pistol type firearm 11 similar to a Glock brand 9 mmpistol commercially available from the Glock, Inc. company of Smyrna,Ga. The firearm includes an elongated barrel 12 extending between adistal muzzle (not shown) and a proximal chamber 13 for holding anammunition cartridge 15 during firing. Additional cartridges 14 aresuccessively loaded from a magazine 16 into the chamber by operation abolt 20 which reciprocatingly slides 21 along an axis 9 substantiallyparallel to the barrel. The distal end of the bolt can have acounterbore forming a seat 23 for nesting the proximal base or rim 17 ofthe cartridge casing 18 during the firing and extraction stages of thefiring cycle. The bolt also carries a firing pin (not shown) whichaxially strikes the primer set into the cartridge base to initiate thefiring of the cartridge.

Except where otherwise noted, the terms “axial”, “axially”, “radial”,and “radially” are in reference to the bolt 20 sliding axis 9. Further,“front”, “forward” and “forwardly” can be used to denote the distal partof a structure or the distal direction toward the muzzle, and “rear”,“rearward” and “rearwardly” can be used to denote the proximal part of astructure or the proximal direction opposite from the distal direction.

An extractor assembly 30 is secured to the bolt 20 near its distal end24. The extractor assembly includes an oblong, rigid rocking member 31pivotably secured to the bolt by a pivot 40 allowing rotation 42 of themember about a pivot axis 41 substantially perpendicular to the slidingaxis 9 of the bolt. Thus the rocking member has a reciprocatingdirection of movement which lies within a plane that can include thebolt axis. The pivot can be formed by a pivot pin defining the pivotaxis of rotation. The pivot pin can be a substantially cylindrical postrotatively engaging a substantially cylindrical bearing.

The rocking member 31 can have a pair of arms 33,34 straddling thepivot. A first, distal arm 33 extends substantially axially distallyterminating in a hook structure 35 at its distal end. A second, proximalarm 34 extends substantially axially proximally terminating in aproximal end 36. In this way, when the rocking member proximal end movesradially outward, the distal, hook end moves radially inward withrespect to the bolt sliding axis 9. A compression spring 60 capturedwithin a pair of opposed wells 38,39 formed into corresponding surfacesof the bolt and proximal arm of the extractor member biases the proximalend of the member radially outward so that the hook structure iscorrespondingly biased radially inward. The spring has a first terminus61 which bears against the bolt and a second terminus 62 which bearsagainst the proximal arm of the extractor member.

The extractor member 31 can reside substantially within a commensuratelyshaped recess 50 formed into a radially outward portion of the bolt 20so that a radially outward surface 44 of the extractor member can besubstantially flush with the radially outward surface 45 of the bolt inorder to further reduce wear and the potential for jamming. Further, thedistal face 47 of the extractor member is substantially coplanar withthe upper distal face 48 forming the strike surface of the boltbordering the counterbore 23 which is furthest from the magazine 16.

The extractor member 31 can have a medial support 51 for carrying thepivot 40 at a position radially inward from the proximal arm 34 and thedistal arm 33 so that the center of rotation is closer to the centerlineof the bolt 20 which can enhance the distribution of loads on theextractor mechanism. The shape and dimensioning of the recess 50 isselected to create a gap 52 between the member arms and the bolt,allowing the limited rocking movement of the member in order to helpaccommodate the variability in cartridge and firearm parts describedabove. The compression spring 60 applies, through the pivot 40 aradially inward biasing force F against the cartridge casing 18 to biasthe rim 17 against the wall structures 19,58 at the periphery of thecounterbore seat 23.

The hook 35 is shaped, dimensioned and positioned axially to engage andbear against the circumferential groove 22 axially separating theproximal rim 17 of the cartridge 15 from the rest of the casing 18. Thusthe hook will have an axial dimension less than the axial dimension ofthe circumferential groove. The hook can have a concave arcuate tip 54shaped and dimensioned to intimately nest against a convex surface ofsaid circumferential groove. Thus the arcuate tip and circumferentialgroove can have commensurate radii of curvature. The hook can alsoinclude a pair of rounded, convex corners 55,56 at the angularextremities of the arcuate tip to reduce the potential for jamming. Inthis way the biased hook of the extractor mechanism can both axially andradially load the casing against the counterbore relief structures inorder to captivate or retain the rim of the casing during extraction anduntil ejection. The dimensioning of the extractor is selected so thatthe hook at the engagement end of the extractor rests at a locationsmaller in diameter than when a cartridge is seated on the boltcounterbore. In other words the there is a snap-fitting type arrangementbetween the rim of the cartridge and the counterbore seat.

As shown in FIG. 3, the distal face 48 forming the impact surface of thebolt 20 is located an axial distance distally D1 from the lower lip 49closest to the magazine, which itself is located and axial distance D2from the counterbore seat 23. The lower lip is supported by a distallyprojecting pedestal 57 radially adjacent to a lower edge of thecounterbore seat 23. The distal face of the bolt, the lower lip, and thecounterbore seat can all reside substantially within planes P1,P2,P3parallel to one another and perpendicular to the sliding axis 9 of thebolt. This axially relieved lip on the lower edge of the distal end ofthe bolt, and the corresponding wall structures on the periphery of thecounterbore seat, help provide greater control over the cartridge 15 asit is being stripped from the magazine and chambered. The lip includes aconcave arcuate wall 58 facing radially inwardly which is shaped anddimensioned to nest against a convex surface of the cartridge rim 17.

The axially relieved lip and counterbore form an arcuate, partial,distally projecting, upper guidewall 19 on the upper portion of the boltdistal end. The guidewall and cartridge rim edge can have commensurateradii of curvature. The guidewall can extend in an angularly limitedmanner around the upper periphery of the counterbore seat terminating ina pair of lateral guides 61,62 at the angular extremities of theguidewall, and leaving an angular gap around the lower periphery of theseat. The lip, guides, and hook serve to guide the rim of the cartridgeinto the seat in a smooth scooping or funneling manner as the cartridgeis stripped from the magazine and chambered.

As stated above and as shown in FIG. 4, the location of the extractionmechanism 30 can be attached to the bolt 20 at a location where theplane of the rocking motion Pr forms a non-zero angle A with thevertical plane Pv of the firearm. For many handgun style firearms wherespace is limited, the angle of the rocking plane from vertical withrespect to the firearm in a upright orientation can preferably bebetween about 65 degrees and about 70 degrees, more preferably bebetween about 66.5 degrees and about 68.5 degrees, and most preferablyabout 67.5 degrees.

Referring now to FIG. 5, during firing, rapidly expanding gasses 70propel the projectile portion 71 of the cartridge distally along thebarrel 12 and out the muzzle. This same gasses can propel the spentcartridge casing 18 in the proximal direction to extract it from thechamber 13 and push the bolt 20 rearwardly. Since the base of the casingis bearing against the seat of the bolt, both the casing and bolt aredriven proximally. It shall be understood that the relative locations ofthe projectile and bolt are shown for illustrative purposes and may notaccurately reflect their actual positions at any given time. The hook 35of the extractor rocking member 31 remains engaged into thecircumferential groove at the rear end of the casing to securely hold itagainst the counterbore seat 23 of the bolt during blowback extractionof the casing from the chamber, and prior to ejection of the case fromthe firearm.

In FIG. 6, the expanding gasses 70 and the momentum of the bolt 20 movethe bolt further in the proximal direction along the bolt sliding axis 9so that the casing 18 has an axial position in line with a radial exitport 75. An ejector causes the casing to dislodge from the counterboreseat 23 and be ejected from the firearm. The ejector can be a mechanicalejector as shown in FIG. 13 in connection with an alternate embodiment,or through Direct Gas Impingement (DGI) which provides a radialcomponent to the expanding gas forces which dislodge and ejects thecasing. At this time the force of the compression spring 60 has beenovercome, allowing the rocking member 31 to rotate such that the hook 35moves radially outwardly.

In this way the above described embodiments achieve a cartridgeextractor which operates over a wide range of cartridge and bolttolerances, has low force absorption during loading, and achievespositive and consistent retention of the cartridge during ejection fromthe firearm.

Referring now to FIGS. 7-13 there is shown an alternate exemplaryembodiment of the invention. The interconnections of the main componentsof this invention are the extractor (FIG. 7, 110), the pivot pin (FIG.8, 220), the compression spring (FIG. 8, 230), and the bolt (FIG. 7,140). This blow-back bolt extractor is a stark departure from prior artbeam flexure designs currently employed by all firearms manufacturers inthe market. This novel application utilizes a compression spring (FIG.8, 230) at the opposite end from the cartridge (FIG. 8 250), with apivot in the middle (FIG. 8, 220) offering a wider range of radialoperation with a flatter rate for spring force encountered. This lowerrate of spring force encountered by the cartridge (FIG. 9, 350) whileloading offers the ability to physically load the extractor (FIG. 10,410) axially against the cartridge (FIG. 10, 450) to restrain theopposite side of the cartridge rim against the counter bored cartridgeseat (FIG. 10, 465) within the bolt (FIG. 10, 440).

This extra cartridge restraint maintains a more consistent control overthe cartridge during the blow-back stage of the firing cycle of thefirearm immediately after firing until the ejector (FIG. 13, 770)engages the cartridge (FIG. 13, 750) to eject the cartridge from thefirearm to ready for the next loading and firing cycle. Alternately,instead of a compression spring biasing the proximal extractor arm awayfrom the bolt, an extension spring can bias the distal extractor arm outtoward the bolt. In other words, instead of the described compressionspring pushing out from bolt centerline under the extractor at theopposite end of the cartridge end of the extractor, an extension springpulling the cartridge end of the extractor in toward the bolt centerlinecan be used. Alternate variations would be of any pivoting extractornon-beam or leaf spring extractor pocketed into a blow-back bolt.

Upon the bolt being released from the ready position (FIG. 11, 540), thebolt moves toward the barrel (FIG. 11, 560) and strips a cartridge (FIG.11, 550) from the magazine (FIG. 11, 552) and moves it toward the barrelchamber (FIG. 11, 562). At first contact between the bolt (FIG. 11, 540)and the cartridge (FIG. 11, 550), the extractor (FIG. 11, 510) is notactuated. Roughly one-halfway through the cartridge chambering cycle thecartridge (FIG. 10, 450) rises vertically sufficiently to contact theextractor (FIG. 10, 410). In the strip-lip (FIG. 9, 312) style of boltshown, this actuation of the extractor (FIG. 9, 310) is accomplished bythe radial movement of the cartridge (FIG. 9, 350) as it is scooped uptoward the bolt centerline as the bolt moves the cartridge (FIG. 9, 350)to final seating within the barrel chamber (FIG. 9, 362). As the bolt(FIG. 12, 640) moves the cartridge (FIG. 12, 650) into the fullychambered position (FIG. 12, 652), the cartridge rim is physicallybiased, or loaded against the opposite wall of the bolt recess for thecartridge (FIG. 10, 465).

Upon firing of the cartridge round, part of the expelled energy from thefired cartridge is utilized in moving the firearm bolt rearward forcartridge casing ejection, and positioning of the bolt for re-chamberinganother cartridge round. This force is transferred through the rearwardmovement of the cartridge, then to the forceful rearward movement of thebolt by the cartridge blow-back. The extractor maintains control of therear of the cartridge at the rim while the kinetic energy of the firedcartridge round moves the cartridge, bolt, extractor, pivot and springrearward. At a specified position in the ejection stage of the firingcycle, the control of the cartridge by the extractor and bolt isovercome by an additional force of an ejector that strips the cartridgecasing from the bolt and extractor retention in order to expel it fromthe firearm. For direct gas impingement firearms, pressurized firinggasses can be channeled to provide radial forces necessary to accomplishejection. For bolts without the strip-lip type of dual plane (FIG. 9,312) cartridge contact face, extractor engagement is later in theloading cycle with an axial engagement to the extractor as the cartridgemoves axially into the counter bored cartridge retaining position.

In this way the extractor helps retain relative alignment of thecartridge case to the cartridge counterbore seat on the distal end ofthe bolt during extraction and prior to cartridge ejection.

FIGS. 7-13 illustrate a cartridge extractor, which comprises the bolt,extractor, and compression spring implemented on a blow-back style offirearm bolt modified to accept a direct gas impingement style ofoperation. The extractor is based in part on the style of an AR-15 orM-16 type of extractor to retain relative alignment of the cartridge tothe cartridge counterbore in the bolt during cartridge ejection. Acompression spring loads the extractor against cartridge, and cartridgeagainst the cartridge counterbore within the bolt. A blow-back style offirearm bolt is thus modified to accept a Direct Gas Impingement styleof cartridge extractor. The bolt in general looks and functions muchlike any other blow-back bolt such as a Glock or Colt with the exceptionthat the extractor is not of a leaf spring type of design as used inprior art designs. The present exemplary embodiment has modificationswithin to allow the utilization of Direct Gas Impingement (DGI) style ofthe DGI bolt carrier group extractor such as that used by the AR-15 orM-16 firearms. The bolt is deviating from the high force bent beamextractor of the traditional blow-back bolts. The present exemplaryembodiment bolt is machined for a pivot pin and pocketed for clearancefor an AR style of extractor.

The present exemplary embodiment provides an extractor based in part onthe style of an AR-15 or M-16 type of extractor to retain relativealignment of the cartridge to the cartridge counterbore in the boltduring cartridge ejection. The extractor is of a design created for thetotally different operating Direct Gas Impingement (DGI) system. Inprior art utilization this extractor operates within the bolt carriergroup wherein this extractor is captivated between the bolt and boltcarrier, and limited in outward movement by the bolt carrier.

The DGI version imparts axial loading to the cartridge only forextraction. In the present exemplary embodiment the blow-back boltextractor operates within the modified bolt only, and imparts radialloading of the cartridge against the counterbore relief of the bolt aswell as axial loading for overall retention and control during cartridgeejection, and is unrestrained at ejection when the bolt istelescopically unrestrained by the first rearward movement of the boltcarrier.

The present exemplary embodiment utilizes this pivoting extractor designthat is preloaded against the cartridge with a compression spring tooffer a greater operational travel with a flatter force deviation thanthe prior art blow-back bolts utilizing a bending beam, thus deviatingfrom the high force bent beam extractors of traditional blow-back bolts.The present exemplary embodiment provides an extractor having a lowforce pivoting design biased into the retention position by acompression spring offering less interference force to the cartridge,and less flexural fatigue to the spring.

In the present exemplary embodiment the compression spring loads theextractor against cartridge rim. The spring can be a conventionalcompression spring on the opposite end of the pivot that loads theengagement end of the extractor against the cartridge at the extractionrim. Alternately, the spring force can be accomplished by an extensionspring on the other side.

As to a further discussion of the manner of usage and operation of thepresent invention, the same should be apparent from the abovedescription. Accordingly, no further discussion relating to the mannerof usage and operation will be provided. With respect to the abovedescription then, it is to be realized that the optimum dimensionalrelationships for the parts of the invention, to include variations insize, materials, shape, form, function and manner of operation, assemblyand use, are deemed readily apparent and obvious to one skilled in theart, and all equivalent relationships to those illustrated in thedrawings and described in the specification are intended to beencompassed by the present invention. Therefore, the foregoing isconsidered as illustrative only of the principles of the invention.Further, since numerous modifications and changes will readily occur tothose skilled in the art, it is not desired to limit the invention tothe exact construction and operation shown and described, andaccordingly, all suitable modifications and equivalents may be resortedto, falling within the scope of the invention.

Although the above embodiment or embodiments of the invention have beendescribed in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the description orillustrated in the drawings. The invention is capable of otherembodiments and of being practiced and carried out in various ways.Also, it is to be understood that the phraseology and terminologyemployed herein are for the purpose of the description and should not beregarded as limiting.

While the exemplary embodiments of the invention have been described,modifications can be made and other embodiments may be devised withoutdeparting from the spirit of the invention and the scope of the appendedclaims.

What is claimed is:
 1. In a firearm having a bolt reciprocatinglysliding axially along a bolt axis, said bolt temporarily engaging anammunition cartridge at a distal bolt seat during a firing cycle,wherein said ammunition cartridge includes a case portion having aproximal rim adjacent to a circumferential groove, an improvement whichcomprises: an extractor assembly which comprise: an oblong rockingmember comprising a hook radially moveable with respect to said bolt;and, said oblong rocking member being pivotingly secured to said bolt ata pivot.
 2. The improvement of claim 1, wherein said hook is biasedradially inwardly by a biasing force.
 3. The improvement of claim 2,wherein said biasing force is overcomeable by an ejector selected fromthe group consisting of a mechanical ejector, and direct gas impingementof pressurized gaseous forces generated during said firing cycle.
 4. Theimprovement of claim 3, wherein said pressurized gaseous forces comprisea radial component impacting said case portion during an ejection stageof said firing cycle.
 5. The improvement of claim 2, which furthercomprises a spring between said bolt and said rocking member, saidspring providing said biasing force.
 6. The improvement of claim 5,wherein said rocking member comprises: a distal end portion carryingsaid hook; a proximal end portion; and, a medial portion secured to saidpivot.
 7. The improvement of claim 6, wherein said spring comprises afirst terminus bearing against said bolt and a second terminus bearingagainst said proximal end portion of said extractor member.
 8. Theimprovement of claim 7, wherein said pivot comprises a pivot pindefining an extractor axis of rotation; said pivot pin having asubstantially cylindrical post rotatively engaging a substantiallycylindrical bearing.
 9. The improvement of claim 8, wherein saidextractor axis of rotation is perpendicular to said bolt axis.
 10. Theimprovement of claim 1, wherein said rocking member moves within arecess formed into said bolt.
 11. The improvement of claim 1, whereinsaid rocking member rocks within a plane angularly inclined betweenabout 66.5 degrees and about 68.5 degrees from vertical with respect tothe firearm in a upright orientation.
 12. The improvement of claim 1,wherein said hook comprises a concave arcuate tip shaped and dimensionedto intimately nest against a convex surface of said circumferentialgroove; and, wherein said concave arcuate tip is further dimensioned tohave an axial dimension less than the axial dimension of saidcircumferential groove.
 13. The improvement of claim 12, wherein saidarcuate tip and curved outer surface of said cartridge have commensurateradii of curvature.
 14. The improvement of claim 13, wherein said hookfurther comprises a pair of convex corners at the angular extremities ofsaid arcuate tip.
 15. In a method for securing a spent ammunitioncartridge case against a seat of a bolt during a firing cycle prior toejection of said case from a firearm, said cartridge case having aproximal rim adjacent to a circumferential groove, an improvement whichcomprises: contacting a proximal rim of said case against said seat;and, simultaneously to said contacting, engaging said circumferentialgroove of said case by a hook of an extractor member pivotingly mountedto said bolt.
 16. The improvement of claim 15, which further comprisesradially biasing said hook against said case.
 17. The improvement ofclaim 16, wherein said radially biasing occurs with a force overcomeableby direct gas impingement forces generated by during said firing cycle.